string — a string designator. For nstring-upcase, nstring-downcase, and nstring-capitalize, the string designator must be a string.

start, end — bounding index designators of string. The defaults for start and end are 0 and nil, respectively.

cased-string — a string.

string-upcase, string-downcase, string-capitalize, nstring-upcase, nstring-downcase, nstring-capitalize change the case of the subsequence of string bounded by start and end as follows:

string-upcase

string-upcase returns a string just like string with all lowercase characters replaced by the corresponding uppercase characters. More precisely, each character of the result string is produced by applying the function char-upcase to the corresponding character of string.

string-downcase

string-downcase is like string-upcase except that all uppercase characters are replaced by the corresponding lowercase characters (using char-downcase).

string-capitalize

string-capitalize produces a copy of string such that, for every word in the copy, the first character of the “word,” if it has case, is uppercase and any other characters with case in the word are lowercase. For the purposes of string-capitalize, a “word” is defined to be a consecutive subsequence consisting of alphanumeric characters, delimited at each end either by a non-alphanumeric character or by an end of the string.

nstring-upcase, nstring-downcase, nstring-capitalize

nstring-upcase, nstring-downcase, and nstring-capitalize are identical to string-upcase, string-downcase, and string-capitalize respectively except that they modify string.

For string-upcase, string-downcase, and string-capitalize, string is not modified. However, if no characters in string require conversion, the result may be either string or a copy of it, at the implementation’s discretion.

 (string-upcase "abcde") → "ABCDE" 
 (string-upcase "Dr. Livingston, I presume?") 
→ "DR. LIVINGSTON, I PRESUME?" 
 (string-upcase "Dr. Livingston, I presume?" :start 6 :end 10) 
→ "Dr. LiVINGston, I presume?" 
 (string-downcase "Dr. Livingston, I presume?") 
→ "dr. livingston, i presume?" 

 (string-capitalize "elm 13c arthur;fig don't") → "Elm 13c Arthur;Fig Don'T" 
 (string-capitalize " hello ") → " Hello " 
 (string-capitalize "occlUDeD cASEmenTs FOreSTAll iNADVertent DEFenestraTION") 
→  "Occluded Casements Forestall Inadvertent Defenestration" 
 (string-capitalize 'kludgy-hash-search) → "Kludgy-Hash-Search" 
 (string-capitalize "DON'T!") → "Don'T!"    ;not "Don't!" 
 (string-capitalize "pipe 13a, foo16c") → "Pipe 13a, Foo16c" 

 (setq str (copy-seq "0123ABCD890a")) → "0123ABCD890a" 
 (nstring-downcase str :start 5 :end 7) → "0123AbcD890a" 
 str → "0123AbcD890a"

nstring-upcase, nstring-downcase, and nstring-capitalize modify string as appropriate rather than constructing a new string.

char-upcase, char-downcase

The result is always of the same length as string.